Yarn severing device for circular knitting machine



Jan. 6, 1970 P. BOY 3,488,679

YARNSEVERING DEVICE FOR CIRCULAR KNT'TTINC- MACHINE Filed Nov. 14, 1966 4 Sheets-Sheet 1 Fig. I

Jan. 6, 1970 P. BOY $43,579

YARN-SEVERING DEVTCE FOR CIRCULAR KNITTING MACHINE Filed Nov. 14, 1966 4 Sheets-Sheet 2 E g l Jan. 6,1970 P BOY 3,431,62

YARN -SEVERING DEVICE FOR CIRCULAR KNITTING MACHINE Filed Nov. 14, 1966 4 SheecS Sheet 3 Jan. 6, 1970 P. BOY 3,4 ,67

YARN-SEVERING DEVICE FQffCIRCULAR KNITTING MACHINE Filed Nov 14, 1966 4 Sheets-Sheet 4 Fig. 5

United States Patent US. Cl. 66-134 4 Claims ABSTRACT OF THE DISCLOSURE A yarn severing apparatus for a circular knitting machine in which a rotating circular disk knife is supported within the needle cylinder circle for rotation with a dial, and a stationary auxiliary knife cooperatively associated with the rotating knife in self-sharpening engagement for severing a yarn.

This invention relates to a yarn severing attachment for circular knitting machines having a rotating needle cylinder and a rotating disk knife mounted within the needle circle.

In the manufacture of ladies seamless stockings on a single cylinder circular knitting machine, it is necessary to sever the yarns that have been introduced into or taken out of knitting action over selected portions of the stocking as well as over the entire stocking at selected areas.

For such operation, several cutting devices, holding and clamping attachments have come into use and are currently being utilized. Their purpose is to sever or to cut the yarns in such a manner that the yarn ends on the knitted stocking are kept as short as possible. At the same time, the yarn severing attachment mounted on the circular knitting machine is required to be simple and compact especially when used in conjunction with automatic multiple feed circular knitting machines.

It is, for instance, well known to employ a rotary knife which rotates together with the needle cylinder with the rotary knife being equipped with serrations or teeth around the knife circumference which teeth reach close to the needles and to which rotary knife a counter or auxiliary knife is associated to cooperate with the teeth of the rotary knife for yarn severance. The purpose of the teeth along the rotary knife circumference is to catch the yarn that has been placed into or taken out of action by the yarn feed finger and which yarn has been pulled down by the first or the last yarn carrying needle so that it will lie between two adjacent teeth. With the rotation of the needle cylinder, the teeth will carry the yarn to the position where the auxiliary or cooperating knife is located for severing the yarn by means of the cutting action of the teeth of the rotary knife in conjunction or cooperation with the auxiliary knife, as shown in US. Patent No. 2,824,436 and German Patent No. 1,192,774.

In actual practice, however, this cutting attachment has not provided satisfactory results particularly when applied with all types of yarns including reinforcing yarns. It has already been attempted to improve this device to obtain shorter yarn ends by making the rotary knife independent and intermeshing a yarn-receiving and severing plate or plates which are guided suitably in a yarn severing action beneath reciprocating plates which can be displaced in and out by means of a releasable locking mechanism as illustrated in German Patent No. 1,200,463.

However, this attachment is too complicated and unwieldy, and does not avoid all the disadvantages of the previously mentioned attachment as it also employs a circular knife with circumferential teeth. The circumfer- 3,488,679 Patented Jan. 6, 1970 ential teeth achieves the translation or movement of the yarn but has the disadvantage that the yarn is in an oblique position and that, therefore, the yarn ends on the knitted article will be substantially longer on the yarn withdrawal side than on the yarn insertion side of a reinforcement area. Furthermore, there will be an unsatisfactory yarn cutting result since the yarn severance takes place not on the outer circumference of the toothed rotary knife but at the bottom or base of a gap between adjacent teeth where the yarn will be positioned. Furthermore, the cooperating or auxiliary knife also has to touch the space between adjacent teeth of the toothed rotary knife in a planar relation so that it is properly guided and does not hook into the teeth on the rotary knife. Such broad contact requires corresponding accurate machining of the sliding surfaces as well as an accurate adjustment for the mounting linkage of the auxiliary or counter knife.

After extended service, the rotary knives have to be resharpened so that the cooperating auxiliary knife hits precisely against the rotary knife reaching over the teeth of the toothed rotary knife so that a clean and reliable cut is assured.

This invention has, therefore, for its objective to sever the yarns evenly under all circumstances and sufficiently short so that additional trimming of the yarn ends becomes unnecessary by providing a device which excels other yarn severing attachments in simplicity, safety and efficiency. The basic idea is to provide the knife disk about its circumference with a smooth cutting edge which extends or reaches close to or proximate the needles and to which is associated a locally fixed cooperating auxiliary knife. For best results, the cooperating; knife should form an acute angle with the tangent line of the knife disk. Preferably, the knife disk should have the form of a rotary knife ring which is positioned on the dial which supports the transfer bits and rotates with it, and where the dial may be lowered to approach closely to the knitted loops of the stockings which are supported on the needles in order to sever the yarns as close to the fabric as desired.

In order that the yarn is not hindered on its travel path to the cutting position on the dial, the disk knife is equipped with a smooth circular edge which extends over the dial cover plate so that the yarn does not touch the dial cover plate. In a different version of this invention, the disk knife is mounted beneath the transfer bits and the cooperating auxiliary or counter knife is vertically retractable to a position above the dial plate and trans fer bit.

It is also known to mount a rotating disk knife within the needle circle which knife has a smooth circular cutting edge driven and located in a lower part of a concentric support plate over the needle cylinder as shown in US. Patent No. 2,713,254. The cutting edge of this circular knife, however, does not reach to the needles but is retained in spaced relation or completely apart from the needles. The yarns are guided in receiving slits against the knife and severed at a considerable distance from the knitted stitches of the article being knit. Furthermore, the severing is performed without any cooperating or auxiliary counter knife thereby reducing considerably the severing reliability, and this attachment requires frequent resharpening of the circular cutting edge of the disk knife.

It is surprising that by the employment of a disk knife with a circular smooth cutting edge, according to this invention, the extending yarn ends are substantially equal in length on both sides of the reinforced area because the yarn slides forward over the smooth cutting edge and changes from its oblique position by the rotation of the needle cylinder to a radial position on the dial. Since the yarn severance takes place at the outer circumference of the rotary disk knife, the distance to the needles and accordingly the length of the remaining yarn ends are extremely short. The cooperating or auxiliary knife only needs to rest against the cutting edge of the rotary or disk knife so that even after prolonged use no resharpening or readjusting will be necessary as a self-sharpening action occurs.

Further details of the invention will be described by means of the accompanying drawings:

FIG. 1 illustrates the attachment of this invention with the dial and rotary knife mounted thereon;

FIG. 2 is a top plan view, somewhat enlarged, illustrating the action of the insertion and withdrawal of the yarns into the cutting attachment;

FIG. 3 is a partial sectional and end elevational view of a modification of this invention with the rotary knife mounted beneath the dial;

FIG. 4 is an end elevational and partial longitudinal view of another modification of this invention; and

FIG. 5 is a partial transverse sectional view of another modification of this invention.

Referring to FIG. 1, the preferred embodiment of the yarn severing attachment presents a rotary disk knife which consists of an annular knife ring 2 mounted on a dial 1 so that both will rotate together. The knife 2 has a smooth circular cutting edge 21 about its circumference. Apertures on the bottom of the knife will receive securing bolts 3 to retain the knife on the dial 1 so that the knife 2 will revolve with dial 1. The dial 1 is fastened to the lower end of the dial shaft 4 with radially movable transfer bits 5 slidably supported in the dial. A ring 7 is fastened to the dial cover plate 6 serving as an axial guide and base for the annular knife 2. The annular knife 2 also has an upstanding skirt forming a smooth circular edge 22 which extends upwardly over the dial cover plate 6. The purpose of the smooth edge 22 of the annular knife 2 is to prevent the yarns from touching the dial cover plate 6 preventing them from becoming ensnarled or adhering to the cover plate. A boss or arm 9, shown in FIG. 2, is fastened on the dial cover plate 6 to which is mounted an angle lever 10 to which is attached a knife holder 13 together with an auxiliary or counter knife 11 that is resiliently anchored. By means of the helical spring 12, pressure is applied to the auxiliary or counter knife 11 forcing it against the smooth cutting edge 22 which extends to cooperate with the auxiliary knife so that between the tangent line at this cutting edge 21 and the knife 11, an acute angle is formed. The acute angle is formed in the opposite direction of the rotating direction of the annular knife ring 2 whereby the yarns may be caught and severed. Yarn guides 14 and 15 are mounted on the dial cover plate 6 for guiding the threads in the conventional manner.

The attachment of this invention operates as follows: when a yarn is withdrawn from knitting action it extends from the yarn feed finger 16 to the last yarn carrying needle 19, as shown in FIG. 2, and assumes, by means of the continuous rotation of the cylinder, an increasingly oblique position until the yarn F positions itself tangentially relative to the annular knife 2 at the point A. Upon additional rotation of the needle cylinder, the yarn F slides in the direction of cylinder rotation forward along the cutting edge 21 and positions itself, the more it recedes from the yarn withdrawal position, in radial direction to the dial, because it takes the shortest path between the yarn feed finger 16 and the last yarn carrying needle 19. In this position, the yarn comes into the path of the auxiliary or counter knife 11 and is severed closely adjacent the last carrying needle 19. The contact point A of the yarn with edge 22 will then be approximately at the position A, whereas the yarn F will be positioned at F, as shown in FIG. 2. The yarn F is led under a suction nozzle 37 before it is severed, and after severance the loose yarn end is retained in the suction airstream generated from a remote source acting through the suction nozzle 37. Instead of the suction nozzle, other suitable yarn holding or clamping attachments may be utilized.

In a similar manner, the yarn severing functions when the yarn is placed into action upon insertion. The inserted yarn E is received by the needles 18 and carried in cylinder rotation by the first yarn carrying needle 23 in the direction of cylinder rotation. As before, the oblique positioning of the yarn E slides along the cutting edge 21, as the needle cylinder is rotating, in a position radial to the dial 1 but this time is a direction opposite to that of needle cylinder rotation as the yarn E is held by the suction nozzle 37. In a similar manner, as the withdrawn yarn F, the inserted yarn E is thus severed by the cutting device at a very short length extended from the knitted fabric. The severed yarn ends are carried away by the suction airstream of the suction nozzle 37.

It is not essential for the operation of this invention whether the insertion or withdrawal of the yarns is achieved solely by the needles or by activation of the yarn guides.

In order to reduce also the horizontal distance between the knitted fabric and the cutting edge 21 of the annular knife 2 which extends 0r reaches closely adjacent the needles 18 for obtaining very short yarn ends, one can provide the annular ring 2 together with the dial 1 and the dial cover plate 6 for vertical up and down movement. To achieve this, the dial shaft 4 rotates in a sleeve 24 which is bearingly supported in the dial bearing support 25. The dial cover plate 6 is firmly connected to the sleeve 24. Clamping ring 26 firmly surrounds the sleeve 24 at the upper end and bears on the control ring 28 under the action exerted by the spring 27, the control ring 28 being pivotally mounted on the sleeve 24 between the clamping ring 26 and the dial bearing mount 25. FIG. 1 shows the dial 1 in the lowered position only.

For the resumption of normal knitting, it is necessary to lift the dial 1 to position the transfer bits 5 relative to the other knitting instrumentalities to proceed with knitting the stocking in the conventional manner. In the main operating drum, a Bowden wire 29 is actuated which turns the control ring 28 to the left. In this way, the clamping ring 26 is elevated together with the sleeve 24. The vertical movement is transmitted by means of the ball bearing 30 to the wheel 31 that is firmly fastened to the dial shaft 4 which is also lifted. A bolt 32 is fastened to the dial cover plate 6 and reaches into the opening in boss 9 on the dial bearing support 25 which will prevent any rotation or pivotal movement of the dial cover plate 6. During the knitting operation and upon requirement for yarn severance the disk 6 and dial are lowered by a procedure opposite from that described above for elevating the dial 1 to position the yarn severing device into the proper position as shown in FIG. 1.

Disk knife 20 is fastened beneath the dial 1 under the transfer bits 5 as shown in FIG. 3. This construction eliminates the necessity for vertically raising and lowering the dial 1. However, in this embodiment the auxiliary or counter knife 11 cooperatively positioned relative to the disk knife 20 must be raised and lowered vertically by means of a Bowden wire 34 which is operated either from the main cam drum or any other suitable actuating mechanism. In this manner, the auxiliary knife 11 may be elevated from the vicinity of the transfer bits 5 during the time of their operation. A suitable yarn clamping device 35 is provided for engaging and holding the yarns before removal of the yarn ends.

The disk knife utilizing a continuous circular edge does not have to be concentric nor does it have to rotate with the needle cylinder with the same rotational velocity. FIG. 4 illustrates a yarn severing attachment forming another embodiment of this invention on a circular knitting machine of which the knitted stockings are removed upwardly and in which no dial is installed as in the previous embodiments. In this form, the disk knife 200 is rotatably mounted on the cylinder plate 36 and is in the form of a circular disk which is driven by means of the flexible rod 38 or by any other suitable means. In order to position the yarn radially as close as possible at the cutting position, the cutting disk 200 is rotated preferably with a higher velocity than the rotational velocity of the needle cylinder.

The cutting edge of the knife may be oblique upward as shown in FIGS. 1 and 3 or oblique downward as illus trated in FIG. 4 as contrasted with the cutting edge 21 thereby reducing the vertical distance between the needles on which the knitted fabric is suspended and the cutting edge. In this way, the disk knife may be similar to a conical ring 2' as shown in FIG. 5 positioned on the dial cover plate 6 with its upper edge 22' extending over the dial cover plate. The auxiliary or counter knife 11 need not be positioned on the disk knife in a flat or plane position as it is sufiicient for the cutting of the yarns when the knife 11' contacts the disk knife 2' along the cutting edge 21'. The purpose of the positioning of the auxiliary knife 11 in such a manner is that the cutting edge 21 is resharpened without the necessity of any regrinding of the disk knife surface for an exact contact with the auxiliary knife.

What is claimed is:

1. A yarn severing device for a circular knitting machine having knitting instrumentalities and a rotating needle cylinder, including a rotating disk knife supported within the needle circle, said knife having a continuous smooth circular cutting edge which extends or reaches close to or proximate the needles, a stationary auxiliary knife cooperatively in yarn severing engagement and in sliding engagement therewith on said cutting edge, said auxiliary knife being urged yieldably into engagement with said circular cutting edge to receive a yarn to be severed at a predetermined position in the path of yarn travel, said stationary auxiliary knife having an end surface adjacent the rotating disk knife substantially tangent thereto with an extension of the forward edge thereof forming an acute angle with a line tangent to the cutting edge of the rotating disk knife for entrapping a yarn to be severed.

2. A yarn severing attachment for a circular knitting machine as claimed in claim 1, including means for displacing said disk knife vertically into and out of close proximity to the knitted loops of the fabric being knitted and suspended on the needles to sever yarns extending from the knitted fabric.

3. A yarn severing attachment for a circular knitting machine as claimed in claim 2, and wherein said disk knife has a recessed upstanding circular rim.

4. A yarn severing attachment for a circular knitting machine as claimed in claim 1, and a dial positioned to rotate within the needle cylinder, said disk knife rotatably mounted on said dial, transfer lbits radially positioned in said dial above said knife, and means for retracting said auxiliary knife to a position remote from said transfer bits selectively during operation.

References Cited UNITED STATES PATENTS 3,100,977 8/1963 Billi et al. 3,252,307 5/1966 Kaese 66134 3,345,834 10/1967 Parthurn.

Re. 25,584 5/1964 Stack et al.

3,100,976 8/1963 Billi et al. 3,157,036 11/1964- Coile.

3,224,230 12/1965 Dusik et al. 3,228,213 1/1966 Wilson. 3,257,829 6/1966 Parthum.

FOREIGN PATENTS 111,384 7/1964 Czechoslovakia. 1,411,502 8/1965 France.

ROBERT R. MACKEY, Primary Examiner 

